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Patrick van Nieuwenhuizen 创建




if you have a dog or if you ever played fetch with a dog you've probably noticed that after you've really abused that poor animal and run it into the ground probably notice that it started to do something interesting it started panting did you ever stop to ask yourself why dogs pant well here's your chance to answer that question see if you can come up with a reason well it turns out that the main reason that dogs pant is so they don't overheat so let's take a look at how that works let's say here we've got our our favorite little puppy and it's just been running around for an hour and it's panting and it's got its tongue lolling out like they do well what's gonna happen when that dog breathes is gonna breathe in cool outside air let's say on that day it happened to be 70 degrees Fahrenheit and it's gonna breathe out hot air because the air that it breathed in is gonna equilibrator its body and if you don't believe me put up a hand to your mouth as you breathe out and feel how hot the air is that you're breathing out what this means is that the dog is expelling heat every time it breathes because it's taking in something cool and putting out something hot and that heat has to come from somewhere now for dogs this is really important because they can't sweat they have fur coats and they couldn't very well soak those fur coats in sweat every time they want to lose some heat so this is really their best way of getting rid of heat now we humans and I'm gonna try to draw one of we humans over here we humans can sweat as a human with an afro apparently we humans can sweat and so this this method of losing heat by by breathing heavily is definitely less important for us but it actually still happens so just like the dog when we breathe in with the air that we breathe in which technically comes from both the nose and the mouth that air goes into our lungs and in our lungs it divides into all those little alveoli that you heard about that have a huge amount of surface area let me just draw a couple of them here all these tiny alveoli have a huge amount of surface area and that allows all this cool air that you breathe in which I'm drawing here to equilibrate with the temperature of the blood that's passing by these capillaries and so just like the dog when we breathe in air that's let's say 70 degrees Celsius we're going to breathe out air that's pretty much body temperature whoops that should not be Celsius that should be Fahrenheit when we breathe in air that's that's 70 or maybe cooler we are going to breathe out air that's body temperature and if this guy is not having a fever that would be about seven 98.6 degrees Fahrenheit so therefore we can see that getting rid of extra eat is another thing that the lungs can do and we have a fancy word for this we call it thermo thermo meaning heat just like a thermometer measures temperature thermo regulation so you could say it's regulation of the temperature of our bodies so that's another thing that the lungs can do lungs can thermo regulate and you'll note that this is kind of convenient because times when you might be overheating just like this dog times when you might be overheating or when you've done a lot of exercise and when you've done all that exercise you need a lot of oxygen to feed your muscles and at the same time you want to get rid of heat so these two functions of providing oxygen and getting rid of excess heat kind of coincide nicely in the case of exercise because what happens when you exercise is that you start breathing really heavily so at rest you might be breathing about five liters of air per minute meaning that a total of five liters of air is coming in and out of your lungs every minute but while you're doing exercise let's say heavy exercise let's say you're you're running a mile and trying to get a really good time you can easily go up to 50 liters per minute and clearly that is a lot more 10 times more so what that means is you're going to be putting out 10 times more eat through your lungs than when you're resting so it's convenient that when you exercise you get more oxygen by breathing heavily and you also get rid of more heat by breathing heavily